Thursday, June 25, 2015

A customer reported that a returned power supply LJ92-01511A for their 50'' Philips (or Magnavox, it's used in different models from both brands) is not producing Vs after it was serviced by us.

Before returning it to here we asked them to test the board independently as we do (that is, manually power on the board and instruct it to activate Vs) to see if it behaves as it did when it was here.

Customer said he tests the board by disconnecting the sustain boards from it and turning on the TV.

The problem with that approach is that if the main board OR the plasma logic board is bad the power supply may never get instructed to turn on Vs in the first place.

So we made this video to help test the board in standalone mode:

Of course like everything else choosing one alternative over another has its drawbacks too.

Testing without load like this is not an ultimate proof the board is functional since it may fail to operate when loaded. This does indeed happen sometimes, but in our experience it is rare enough to justify saving the overhead of a full blown test.

If a board behaves differently with and without a load then a more careful inspection under load is clearly needed.

And still more often than not the problem would turn out to be in the load and not the power supply - i.e. shorted sustain board in plasma TVs or main board in the LCD/LEDs.